SUPERGEN Wind2011 General Assembly

Connecting offshore wind farms to the onshore grid

by Dr Mike Barnes, University of Manchester

20th March 2011, Durham University

Overview:

Improving system reliability

Key focus at this stage:

– Power electronic converter interactions

• with machine

• with other converters

• with VSC HVDC converter

• with cable and system protection

Goal: better more integrated

system design

The System

Tony

Caroline,

SiyuKevin (Exp Val),

Siyu (Review)

Tasks to Date:

1. DC Link (A Beddard)• DC Breaker review/modelling

• Cable modelling

2. DFIG (Ting Lei)• FMEA of system

• System modelling

3. PMSG / System (Siyu Gao)• Wind farm system review (context)

• PSCAD PMSG modelling

4. Experimental Evaluation (K Dyke)

1. Tony - HVDC Circuit Breakers

Required to clear dc side faults without de-energising grid

Designs generally fall into one of the following categories:-

BRKLs

SA

I Ib

Ic

Is

CL

SLs

SA

I Ib

Ic

Is

C

SA

Ib

Is

Ls

(i) Resonance circuit breaker (ii) Hybrid circuit breaker (iii) Solid-state circuit breaker

• Resonance & Hybrid – Low on-state losses but slow operation• Solid-state – Fast interruption speed but high losses• New design – Compromise between losses and speed

Modelling HVDC Cables

Aims– Ascertain required levels of model fidelity for different study types.

– Determine which model provides necessary fidelity while minimising simulation time

HVDC Modelling Report– Calculation of cable parameters

– Transmission line theory

– Representation of cables (pi-section, distributed parameter, etc)

– Interface cable models in PSCAD (Dommel’s method)- in progress

– Simulations

– Analysis of results

– Conclusions and recommendations

2. Caroline - DFIG Model

Response to Set Demand Changes

Grid Side Converter

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 ...

...

...

-1.20 -0.60 0.00 0.60 1.20 1.80 2.40 3.00 3.60 4.20 4.80

y (

MW

,MV

Ar)

Pstator (MW) Qstator (MVAr)

-0.100

0.600

y (

kV

)

vg_d (kV) vg_q (kV)

-1.00

-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

1.25

y (

kA

)

ig_d ig_q

3. Siyu - Survey on offshore

wind power technologies

Types wind turbines summarized and compared.

Developments of power electronics and grid links summarized.

Installation of different offshore wind turbine foundations and

substations have been studied.

Different generations of offshore substations have been

summarized.

Projections on offshore energy have been made.

Modelling a Direct Drive

PMSG wind turbine

Direct drive permanent magnet synchronous wind turbine is now the

favoured design since it is able to provide better support for the

utility network then conventional DFIG wind turbines.

The model aims to combine the mechanical and electrical properties

of the wind turbine together to give comprehensive simulation

results.

4. Kevin - MIL to HIL

Establish behaviour of HVDC using PSCAD

Use Matlab® Simulink™ to provide simulations for a model-in-loop voltage source inverter

Validate Simulink™ model-in-loop against Hardware-in-loop voltage source inverter

VSI for HIL

Design requirements

Isolated High-bandwidth transducers (voltage, current and temperature) for use in hardware control (DSP) and data acquisition (dSpace)

Isolated High-speed digital lines

Thermal management and protection for flexible control schemes and high speed operation.

Hardware (DSP) managed safety critical control.

CAN bus interface for dSpace commands.

Isolation

Signal Conditioning

Hardware Design

Milestones

Thermal analysis of 6-switch SPWM complete

Thermal solution acquired, forced air cooled bonded fin heat sink

All analogue designs complete

All system critical hardware procured

5. Summary

Progress:

– Background review on multiple areas complete

– Models of DFIG and PMSG progressing

– Validation hardware progressing

– Good interaction with partner companies (Siemens, Alstom Grid, National Grid)